Post-boriding processes for treating pipe and recovering boronizing powder

ABSTRACT

A process comprising:
         placing a boronizing powder composition in a metal pipe comprising a first end, a second end, an inside surface and an outside surface;   heating the pipe to form a borided layer on the inside surface, and spent boronizing powder;   removing the spent boronizing powder from the pipe, thereby forming an empty boronized pipe;   heating the empty boronized pipe to above its austenitizing temperature, thereby forming an austenitized pipe;   quenching the austenitized pipe, thereby forming a quenched pipe;   tempering the quenched pipe, thereby forming a tempered pipe; and   threading the tempered pipe.

FIELD OF THE INVENTION

The invention relates to the post-boriding processing of pipes. Moreparticularly, the invention relates to a method for hardening pipesafter boronizing to improve core mechanical properties, the use ofunthreaded end caps during boronizing to allow for threading of pipeends after boronizing, and for recovery of boronizing powder.

BACKGROUND OF THE INVENTION

Treating metal surfaces is sometimes necessary when the targetedapplication for the metal workpiece subjects the metal to high wear,erosion or corrosion. For example, metal parts in agricultural equipmentare sometimes treated to successfully withstand the erosive demandsrequired during their normal use. Even more demanding applicationsinvolve both erosion and corrosion. Such an application is embodied inthe oil and gas industry where oil wells are involved. In oil and gasproduction, a sucker rod pump can be used to pump desired products tothe surface for recovery. The pump functions from the surface byoscillating a rod up and down inside a pipe that drives a pump locatedat the bottom of the well. Each upward stroke of the pump transportsliquid containing the targeted product up through a tube towards thesurface. But such environments can be very harsh, with temperatures of250° C. and pressures of 70 MPa or higher not being uncommon. Thepresence of sour crude in the well also means corrosive compounds suchas hydrogen sulfide, carbon dioxide, methane, produced water, producedcrude and acidic conditions will be present. Under the best ofcircumstances, these conditions alone would represent a challenge to apipe operating in such a service, however, the action of the sucker-rodpump complicates it still further, since the rod can wear against theinside surface of the pipe as it moves up and down. This mechanism ofwear removes a portion of the metal tubing's surface layer, exposing theunderlying layer to corrosion. However, the newly corroded layer cannotprotect the pipe from further corrosion since it is swiftly worn away bythe continued action of the pump rod. Thus, an undesirable, repetitivecycle of erosion/corrosion/erosion takes place that can rapidly causethe pipe to fail. Since environmental concerns in recent years havepushed drilling rigs into deep water, further away from coastlines, theimplications of pipe failure are very serious. Thus, oil producers havepreferred treated pipe for pumping applications, particularly, thediffusion-based treatments such as nitriding, carburizing and boriding.However, while nitriding and carburizing can produce hard metalsurfaces, they do not harden as well as boronizing, which creates a wearlayer with higher hardness than many wear resistant thermal spraycoatings, such as tungsten carbide and chrome carbide. The boron is notmechanically bonded to the surface, but instead is diffused below thesurface of the metal, making it less prone to delamination, peeling andbreaking off treated parts. Just as importantly, these other methodscannot provide the corrosion resistance that boronizing offers.

Several methods for boronizing metal articles are available. Forexample, liquid boriding techniques can be employed, where electrolyticor electro-less baths are employed to deposit layers of borides. Gasboriding or plasma boriding can also be used. However, these methods,while having certain advantages, are unsuitable for environmentalreasons or are impractical for long tubing. Paste-boriding is aparticular type of selective boriding, where the boronizing compositionis applied as a paste to the metal surface, and then heated. Thistechnique, while being useful for localized spot boriding, is completelyunsuitable for pipes because there is no practical way of applying thepaste through the length of the pipe. Powder pack boronizing, typicallyreferred to as “pack cementation” boronizing, involves placing a metalpart in physical contact with the boron source as part of the boronizingpowder composition. For example, a metal part can be buried in aquantity of powder, or a pipe can be filled with powder so it contactsthe pipe's interior surface, and the pipe is heated.

Powder boronizing compositions typically contain a boron source, anactivator, and often a diluent, where reactive boron-containingcompounds such as amorphous boron, crystalline ferro-boron, boroncarbide (B₄C), calcium hexaboride (CaB₆), or borax react with ahalide-based activator upon heating to form gaseous boron tri-halides,such as BF₃ or BCl₃, which react with the metal surface to deposit boronon the surface, which is then able to diffuse into the metal structure.Diluents are included to provide bulk and reduce cost.

Conventional boronizing of pipes typically involves manual pipehandling, where there is an excess of exposure to powder compositionsand boronizing gas by operations personnel during the loading andoff-loading process. Many boriding powder compositions are also prone tosintering to a solid cake inside of a pipe that is difficult to breakapart and remove after boriding. It has unexpectedly been found that itis possible to minimize operator exposure to powder and boronizing gasesthrough a closed system of powder movement, as well as the use of ananti-sintering agent for the powder, to prevent sintering and caking ofpowder inside the tubing making it easier to remove after boriding.

Conventional pipe boronizing for oil field applications has beenperformed where the pipes are boronized and treated to conform to theAmerican Petroleum Institute's API 5CT specification's grade J55. Therequirements for J55 grade tubing listed in API 5CT Table E.5 are 55-80KSI yield strength, 75 KSI minimum tensile strength and no hardnessrequirement. The J55 tubing does not have as high of yield strength oras high of burst pressure as what many petroleum companies desire;however, to date boronized tubing has only been offered in the J55grade. The yield strength and burst pressure of the J55 tubing isconsidered marginal in many wells and oil producers would prefer to havea higher grade of boronizing tubing with higher levels of yield strengthand burst pressure for a greater safety factor when operating at highpressures and high temperatures. Higher strength grades such as L80,N80, R95, M65, C90, T95, C110, P110, and Q125 are all produced byperforming a heat treatment involving austenitizing, quenching andtempering, and all have higher strength properties than J55 gradetubing. L80 is a commonly used grade of tubing in oil producing wells.The core mechanical properties of L80 grade are 80-95 KSI yieldstrength, 95 KSI minimum tensile strength, and 23 HRC maximum hardness.In many wells, the entire string of tubing/piping used will be L80 gradetubing for its higher strength and burst pressure properties, butboronized tubing that only meets J55 grade requirements is often used atthe bottom of the wells as it has improved wear and corrosionresistance. However, as discussed above, the J55 grade tubing does nothave the same high strength and burst pressure ratings compared to L80grade tubing, and this reduces the pressures that oil producers mayoperate at within the wells, and further reduces the safety factorsavailable to oil producers. It has unexpectedly been found thatboronizing and post-boride hardening of pipe is possible if reheating isperformed using processing parameters that do not adversely affect theintegrity of the boride layer. This allows the tubes to be heat treatedto meet the API 5CT L80 specification for yield strength and burstpressure while also having a boride layer present on the inner bore toincrease wear and corrosion resistance.

Oil field production tubing typically consists of a long pipe withflared ends that have external threaded connections at each end suchthat they can be joined together using short internally threadedcouplings into long tubing strings. To date, boronizing of tubing foroil wells has been performed by screwing a closed cap onto one threadedend connection of a pipe, filling that pipe with boronizing powder untilfull, and then screwing a second closed cap onto the other threadedconnection end of the pipe to contain the boronizing powder inside thepipe during the process. One issue with this practice is that theboronizing process involves heating pipe to high temperatures such as1400 F to 1750 F for many hours and the threads are soft and have littlestrength at these temperatures. Any forces or stresses placed onto thesethreads by the screwed on end cap can cause the threads to bend and warpduring high temperature boriding. High temperature creep strength isalso very low in these threads and they can warp and distort from theheating and cooling process alone as the metal expands during heating,contracts during cooling and may warp under any stresses present.Threads are also prone to damage as they can be easily nicked, dingedand damaged during installation of the caps, removal of the caps,handling and transport of the pipes and subsequent cleaning andstraightening operations after boriding. For these reasons, many oilproducers have encountered problems with making good threadedconnections and thread leakage on boronized pipes produced with threadspresent on the tubing during the boriding process. The development of aboriding process that can be performed on an unthreaded pipe using newcap designs that can attach to the ends of a pipe without requiring athreaded connection would allow for the threading operation to beperformed after boriding which would yield higher quality threads thatwould not be subject to high temperature distortion and warpage andcould not be damaged during the processing if not present duringboriding.

SUMMARY OF THE INVENTION

In one embodiment, the subject matter of the present disclosure relatesto a process comprising placing a boronizing powder composition in ametal pipe comprising a first end, a second end, an inside surface andan outside surface; heating the pipe to a temperature to form a boridedlayer on the inside surface, and spent boronizing powder; removing thespent boronizing powder from the pipe, thereby forming an emptyboronized pipe; heating the empty boronized pipe to above itsaustenitizing temperature, thereby forming an austenitized pipe;quenching the austenitized pipe, thereby forming a quenched pipe; andtempering the quenched pipe, thereby forming a tempered pipe.

In another embodiment, the subject matter of the present disclosurerelates to a pipe produced by a process comprising placing a boronizingpowder composition in a metal pipe comprising a first end, a second end,an inside surface and an outside surface; heating the pipe to a boridingtemperature, thereby forming a borided layer on the inside surface, andspent boronizing powder; removing the spent boronizing powder from thepipe, thereby forming an empty boronized pipe; heating the emptyboronized pipe to above its austenitizing temperature, thereby formingan austenitized pipe; quenching the austenitized pipe, thereby forming aquenched pipe; and tempering the quenched pipe, thereby forming atempered pipe.

In still another embodiment, the subject matter of the presentdisclosure relates to a boronized pipe meeting the specification of API5CT specification Grade L80.

In an embodiment, the subject matter of the present disclosure relatesto a process for treating a boronized pipe comprising a borided layer onits interior surface, the process comprising: heating the boronized pipeto above its austenitizing temperature, thereby forming an austenitizedpipe; quenching the austenitized pipe, thereby forming a quenched pipe;and tempering the quenched pipe, thereby forming a tempered pipe.

In another embodiment, the subject matter of the present disclosurerelates to a pipe produced using a process for treating a boronized pipecomprising a borided layer on its interior surface, the processcomprising: heating the boronized pipe to above its austenitizingtemperature, thereby forming an austenitized pipe; quenching theaustenitized pipe, thereby forming a quenched pipe; and tempering thequenched pipe, thereby forming a tempered pipe.

In another embodiment, the subject matter of the present disclosurerelates to a process comprising heating a boronized pipe to above itsaustenitizing temperature, thereby forming an austenitized pipe; andquenching the austenitized pipe, thereby forming a borided and quenchedpipe.

In still another embodiment, the subject matter of the presentdisclosure relates to a pipe produced by a process comprising heating aboronized pipe to above its austenitizing temperature, thereby formingan austenitized pipe; and quenching the austenitized pipe, therebyforming a quenched pipe.

In another embodiment, the subject matter of the present disclosurerelates to a process comprising placing a boronizing powder compositionin a metal pipe comprising a first end, a second end, an inside surfaceand an outside surface; heating the pipe to a boriding temperature,thereby forming a borided layer on the inside surface, and spentboronizing powder; and removing the spent boronizing powder from thepipe, wherein the spent boronizing powder is removed from the metal pipewith a closed transport system.

In an embodiment, the subject matter of the present disclosure relatesto a process comprising placing a boronizing powder composition in ametal pipe comprising a first end, a second end, an inside surface andan outside surface; heating the pipe to a boriding temperature, therebyforming a borided layer on the inside surface, and spent boridingpowder; and removing the spent boriding powder from the pipe, whereinthe boronizing powder is placed in the metal pipe by conveying thepowder to the pipe using a closed transport system selected frompneumatic conveying, rotary valve, screw conveyer or combinationsthereof.

In still another embodiment, the subject matter of the presentdisclosure relates to a process comprising placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to a boridingtemperature, thereby forming a borided layer on the inside surface, andspent boriding powder; and removing the spent boriding powder from thepipe, wherein the boronizing powder is placed in the metal pipe byconveying the powder to the pipe using a closed transport system, andthe spent boronizing powder is removed from the metal pipe by a closedtransport system.

In an embodiment, the subject matter of the present disclosure relatesto a process comprising transporting oil or gas in an oil well with apipe produced by a process comprising placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to a boridingtemperature, thereby forming a borided layer on the inside surface, andspent boronizing powder; removing the spent boronizing powder from thepipe, thereby forming an empty boronized pipe; heating the emptyboronized pipe to above its austenitizing temperature, thereby formingan austenitized pipe; quenching the austenitized pipe, thereby forming aquenched pipe; and tempering the quenched pipe, thereby forming atempered pipe.

In an embodiment, the subject matter of the present disclosure relatesto a process comprising transporting oil or gas in an oil well with apipe produced by a process comprising treating a boronized pipecomprising a borided layer on its interior surface, the processcomprising: heating the boronized pipe to above its austenitizingtemperature, thereby forming an austenitized pipe; quenching theaustenitized pipe, thereby forming a quenched pipe; and tempering thequenched pipe, thereby forming a tempered pipe.

In still another embodiment, the subject matter of the presentdisclosure relates to a process comprising placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to form aborided layer on the inside surface, and spent boronizing powder;removing the spent boronizing powder from the pipe, thereby forming anempty boronized pipe; heating the empty boronized pipe to above itsaustenitizing temperature, thereby forming an austenitized pipe;quenching the austenitized pipe, thereby forming a quenched pipe;tempering the quenched pipe, thereby forming a tempered pipe; andthreading the tempered pipe.

In another embodiment, the subject matter of the present disclosurerelates to a process comprising boronizing an unthreaded pipe, therebyforming an unthreaded boronized pipe; and threading the unthreadedboronized pipe.

In an embodiment, the subject matter of the present disclosure relatesto a process for boronizing a metal pipe comprising a flared first end,a second end, an inside surface and an outside surface, the processcomprising: fastening a first split-bushing end cap on the flared firstend; depositing boronizing powder in the pipe; fastening a plate orsecond split bushing end cap on the second end; and heating the pipe toa temperature from 1400° F. to 1900° F., thereby forming a borided layeron the inside surface, and generating spent reaction gases and spentboriding powder.

In another embodiment, the subject matter of the present disclosurerelates to a process for boronizing a metal pipe comprising anunthreaded first end, an unthreaded second end, an interior, an insidesurface and an outside surface; fastening a first plate to the first endof the pipe; placing boronizing powder in the interior of the pipe;fastening a second plate to the second end of the pipe; and heating thepipe to a temperature from 1400° F. to 1900° F., thereby forming aborided layer on the inside surface, and generating spent reaction gasesand spent boriding powder. Typically, the first plate and second plateare fastened onto the ends of the pipe by welding or joining.

In still another embodiment, the subject matter of the presentdisclosure relates to a process comprising placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to form aborided layer on the inside surface, and spent boronizing powder;heating the pipe with the borided layer to above its austenitizingtemperature, thereby forming an austenitized pipe; quenching theaustenitized pipe, thereby forming a quenched pipe; and tempering thequenched pipe, thereby forming a tempered pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure will be more fullyunderstood from the following detailed description, taken in connectionwith the accompanying drawings, in which:

FIG. 1 illustrates a flow diagram for the boronizing of pipes includingthe loading and unloading of boronizing powder compositions.

FIG. 2 illustrates split-bushing end caps and an unthreaded flared tubeend.

FIG. 3 illustrates a split-bushing end cap for an unthreaded flared tubebeing mounted on flared section of tube where the split bushing diameterfits around the main body of the tube but will not be able to slip overthe larger diameter of the flared end of the pipe.

FIG. 4 illustrates the installation of a split-bushing endcap forboronizing unthreaded tubes with the two split bushing piecessurrounding the main body diameter of the pipe. The two split bushingpieces are about to be screwed into the end cap where the split bushingswill be pulled up into the end cap during until inner diameter of thesplit bushings catches on the tapered section of the larger flared enddiameter and secures the end cap and split bushing assembly tightagainst the end of the pipe.

FIG. 5 illustrates a split-bushing end cap installed on the end of aflared tube.

FIG. 6 illustrates a split-bushing from various angles.

FIG. 7 illustrates an end cap from various angles.

FIG. 8 illustrate a plate end cap.

DETAILED DESCRIPTION OF THE INVENTION

The subject matter of the present disclosure provides a process fortreating boronized piping having a particularly designed boride layerthat is physically uniform, i.e., not oxidized, cracked, flaked orpitted. The resulting treated pipe is capable of meeting the stringentrequirements of high strength pipe such as API specification 5CT GradeL80. The subject matter of the present disclosure also provides aprocess for boronizing a metal pipe in an environmentally safe andefficient manner by loading and unloading pipes in a closed transportsystem.

For the purpose of this specification, the terms “boronizing” and“boriding;” and “boronized” and “borided” will be used interchangeablyto designate the boronizing process and pipes resulting from the processof the present subject matter. Also, the terms “pipe” and “tubing” willbe used interchangeably to designate a cylindrical or round-shapedconduit for carrying fluids such as gases, liquids, slurries or powderedsolids. When reference is made to the diameter of a tube or pipe, unlessit is designated differently, it will mean the inside diameter of thetube or pipe. Finally, the term “powder” means a dry, bulk solidcomposed of a large number of very fine particles.

Metal Pipes

The metal pipes or tubes to be boronized preferably have an innerdiameter (ID) of 1.0 to 12.0 inches. More preferably, the pipe has an IDof 1.5 to 6.0 inches. Most preferably, the pipe has an ID of 1.5 to 3.0inches. The outside diameter of the pipe can vary depending on thepressure rating of the pipe that can require different wall thicknesses.The burst pressure rating of the pipe to be boronized can range fromatmospheric to 10,000 psig. The length of the pipe can vary. Preferably,the length of pipe can range from 1.0 to 36.0 feet. More preferably, thelength of the pipe can range from 10.0 to 36.0 feet. Even morepreferably, the length of the pipe can range from 31.0 to 36.0 feet.Alternately, the length of the pipe can range from 14.0 to 18.0 feet.

Normally, the pipe or tube ID is the same along this entire length.However, in some applications, as discussed below, the end(s) of thepipe can be worked in the forging process to upset and enlarge (flare)the ends of the pipe. In this case, the ID of the pipe refers to the IDof the pipe/tube prior to any enlargement of the ends, i.e., the term IDrefers to the ID of the pipe except at the flared ends. The ends of thetube or pipe to be boronized can be threaded or non-threaded. When thepipe is threaded, it is possible to cap the pipe end with acorresponding threaded end cap. Typically, such an end cap is alsospot-welded in place to maintain the cap's position in preventing lossof boronizing powder, while not imposing a tight seal on the pipe. Weresuch a seal imposed on the pipe, the buildup of boronizing gases duringboronizing would overpressure the pipe and result in pipe failure.Preferably, the pipe is non-threaded

Preferably, the ends of the pipe to be boronized are processed in anoperation known as upset ending, which is a forging process where theend of the pipe or tubing is flared and thickened by heating and forcingit through a die and over a mandrel. By processing the tube or pipe inthis manner, the tensile strength of the pipe is enhanced, inanticipation of the expected tensile strength loss when the tube or pipeis threaded. Thus, the flared ends of the pipe or tube have a largeroutside diameter than the predominant outside diameter of the tube orpipe, as shown in FIGS. 4 and 5. The difference in outside diameterbetween the flared and non-flared sections of the pipe is typically 0.25to 0.50 inch. Typically, the length of pipe that is flared is 4 to 6inches. More preferably, the ends of the pipe to be boronized are firstprocessed to be flared as discussed above, and are then threaded afterboronizing.

When the pipe ends are flared but not yet threaded, they may be cappedin a number of ways identical to non-flared pipes. One or both ends maybe flared. When the pipe ends are flared, preferably, both ends areflared. A tight seal of the pipe during boronizing where gas cannotescape is not desired, as it would result in over-pressure of the pipeand pipe damage or failure. For example, a cylindrical cap may be fittedover the pipe end and spot-welded in place. Alternately, the end of thepipe can be filled with high temperature ceramic cloth or metallicwiring to maintain the stability of the boronizing powder and keep itwithin the tube or pipe, but still allow the boronizing gas producedduring the boronizing process to escape the pipe. A split-bushing endcapcan be used when the tube or pipe has a flared end. The split bushingendcap is composed of an end cap portion and a split-bushing portion, asshown in FIGS. 4 and 5. The end cap portion, is typically cylindricaland capped at one end, and has an interior surface that is threaded asshown in FIG. 5. The split-bushing portion is threaded to accommodatethe threading of the corresponding end cap, and is present as at leastone curved section as shown in FIG. 6. Preferably, the split-bushingportion is present as at least two curved sections. Optionally, thecurved section(s) can also have at one end a portion of a metal flange,such that when all the sections are in place on the flared section ofthe tube end or pipe they form a hexagonal nut section. More preferably,the split-bushing portion is present as two curved sections. To cap theflared section of the tube or pipe, the split-bushing portion is placedover the outer diameter of central portion of the tube or pipe justinside the tapered flared end, and the end cap portion is fitted overthe end of the tube or pipe so that the threaded interior of the end capportion engages the threads of the split-bushing portion. FIGS. 4 and 5.The end cap portion is then tightened over the split-bushing portion,fastening it to the flared section of the tube or pipe. Thesplit-bushing endcap can be constructed from any metal compatible withthe temperatures of the boronizing process.

Metals

The metals to be boronized according to the process of the currentsubject matter are generally any that can be boronized. Preferably, themetal article is selected from plain carbon steel, alloy steel, toolsteel, stainless steel, nickel-based alloys, cobalt-based alloys, castiron, ductile iron, molybdenum, or stellite. More preferably, the metalto be boronized are ferrous materials such as plain carbon steels, alloysteels, tool steels, and stainless steel.

Boronizing Process

The boronizing process of the present subject matter is particularlydesigned to provide an excellent boride layer on a metal pipe while alsoensuring minimal powder exposure to operations personnel. This can beaccomplished not only by the use of a particular boronizing composition,but by loading and unloading of the powder from the metal pipe in aclosed system. At the start of the boronizing process, the metal pipemust be filled with boronizing powder, since the boriding reactionsadequately take place only where there is contact of the powder and theinner surface of the pipe. The boronized powder is transferred from astorage drum, hopper or sack that houses powder of the appropriatecomposition. Because a known amount of powder will be necessary to fillthe pipe of a particular inner diameter and length, the metal pipe canbe filled using a closed transport system employing solids meteringsystems such as loss-in-weight feeders, screw feeders, rotary valves ora pneumatic conveyance system. Weigh cells may also be used. When apneumatic conveyance system is used, air or inert gases may be used toconvey the powder. Ancillary lines including closed screw conveyers,piping or hoses can be used to transport the metered boronizing powderto the pipe in the closed transport system as described above. Suchtransport piping is vented to particle separators such as a cyclone orbaghouse. A vacuum pump or ejector can be included in the powder fillsystem to prevent outside exposure of powder.

After the metal pipe is filled with boronizing powder the pipe is heatedin a furnace to achieve a boronizing layer, i.e., a boridingtemperature. Preferably, the pipes are heated to 1400 to 1900° F. Morepreferably, the pipes are heated to 1500 to 1750° F. Preferably, thepipes are typically heated for 1.0 to 24.0 hours. More preferably, thepipes are heated from 4.0 to 16.0 hours. The types of furnaces typicallyused include either open fire or atmosphere controlled furnaces that aregenerally either batch, continuous roller hearth, car-bottom, orpusher-type furnaces.

After the pipe is boronized, the boronized pipe is typically cooled.Then the spent boronizing powder is removed from the metal pipe byremoving end caps, aligning the pipes over a closed spent boronizingpowder collection container, sealing the powder discharge to preventexposure, and the pipes are then vibrated to shake the boronizing powderout of the tubes and into the closed collection container. The removedspent powder can be transported to a storage vessel for spent powders bya closed transport system as described above.

For filling and emptying, the pipe can be equipped with end fittings, asdescribed above. The ends of the pipe, whether flared or non-flared, canbe threaded or non-threaded prior to boronizing. Preferably, the ends ofthe pipe are non-threaded prior to boronizing. For the purposes of thisspecification, the term “threading” or “threads” on a pipe, whetherflared or non-flared, refer to the groves cut into the pipe at its ends,whether on the inside or outside surface of the pipe to allow pipes tobe connected, all performed in accordance with API Standard 5B“Specification for Threading, Gaging, and Thread Inspection of Casing,Tubing, and Line Pipe Threads,” the disclosure of which is herebyincorporated by reference.

In addition to the fittings discussed above, the end fittings can beslip on, flanged or screwed fittings, partially or fully welded, and canbe configured to allow free flow of solids through the pipe end openingto facilitate powder filling or emptying, as well as permitting ventingof boronizing reaction gases for downstream processing during theboronizing process, while minimizing solids movement. The end fittingscan optionally be configured to incorporate valving or manifolding forisolation of powder flow or reaction gas venting. Alternately, if amanual loading/unloading operation is used, the end fittings can bemetal plates as shown in FIG. 8 that are welded to the ends of the pipeto hold the boronizing powder within the pipe during the boronizingprocess. Preferably, the metal plates would be tack-welded to the pipeto ease removal when the boronizing process is completed.

From time to time it may be necessary to change the formulation of theboronizing powder due to a depletion of active components over time,accumulation of large sintered particles, or because of contamination. Apowder recycling system can thus be configured to facilitate theaddition of new powder to that being reused, or individual components ofthe powder compensation that have become depleted.

Boronizing reaction gases result from the boronizing process. Dependingon the type of activator that is used, these gases can includehydrofluoric acid, fluorine, hydrochloric acid, chlorine, BF₃, BCl₃, KF,NaF, or mixtures thereof. The volume of gases will also depend on theamount of activator used in the boronizing composition, where higherlevels of activator correspond to higher levels of reaction gases.

Various boronizing compositions can be used in the process of thepresent subject matter. These compositions typically contain a boronsource, an activator, and optionally a diluent or sintering reductionagent.

Boron Source

The boron source for use in the powder boronizing composition cangenerally be any reactive boron solid capable of reacting with anactivator to form gaseous boron trihalides, such as BF₃ or BCl₃. Thesegaseous compounds react with the surface of the metal to deposit boronon the surface of the workpiece which may then diffuse into the metallicstructure and form an iron-boride compound layer. Preferably, the boronsource is selected from B₄C, amorphous boron, calcium hexaboride, boraxor mixtures thereof. More preferably, the boron source is B₄C.Preferably, the boron source is present in the powder boronizingcomposition in an amount of 0.5 to 4.5 wt %, based on the total weightof the powder boronizing composition. More preferably, the boron sourceis present in the powder boronizing composition in an amount of 2.0 to4.0 wt %. Most preferably, the boron source is present in the powderboronizing composition in an amount of 2.0 to 3.0 wt %. Levels of theboron source less than those recited can result in a poorer qualityboride layer due to thinner boride layers and larger gaps and spacingbetween the teeth in the boride layer that would be occupied by lowerhardness substrate material. Levels of the boron source greater thanthose recited can result in poorer boride layer quality due to formationof a dual-phase boride layer comprised of both FeB and Fe₂B which hasinferior performance characteristics when compared to a single-phaseboride layer comprised of only Fe₂B iron boride.

Activator

The activator for use in the powder boronizing composition can generallybe any halide-containing compound that is capable of reacting with theboron source after heating as described above to form gaseous borontrihalides, such as BF₃ or BCl₃. The boron atoms are then inserted by agas diffusion process into the metal structure. Preferably, theactivator is selected from KBF₄, ammonia chloride, cryolite, sodiumfluoride, ammonium bifluoride, potassium fluoride, calcium fluoride, ormixtures thereof. More preferably, the activator is KBF₄. Preferably,the activator is present in the powder boronizing composition in anamount of 1.0 to 20.0 wt %, based on the total weight of the powderboronizing composition. More preferably, the activator is present in thepowder boronizing composition in an amount of 3.5 to 10.0 wt %. Mostpreferably, the boron source is present in the powder boronizingcomposition in an amount of 4.0 to 6.0 wt %. Levels of activator lessthan those recited can result in a poorer quality boride layer due toformation of voids and porosity in the boride layer. Levels of activatorgreater than those recited can result in excess quantities of spentreaction gas, as described below, which can present environmentalchallenges.

Sintering Reduction Agent

The sintering reduction agent facilitates the operation and ease ofperforming the boronizing process by preventing sintering of the powdercomposition. This is an important consideration in process optimization,particularly in those situations where long, small diameter tubes mustbe boronized, because sintered materials cling to themselves and to thesurfaces of the metal part. It can be a time-consuming process to removethe sintered material, especially in the case when the interior of longpipes is being boronized. Even in the case of simple geometry partsbeing boronized, it can be very challenging to remove parts from asintered block of boronizing powder after the process is complete, whichforms if the boronizing powder does not contain a sintering reductionagent. Very small parts can also be lost in the sintered boronizingpowder which is not readily ground or crushed back down to loose powderthat can be sifted and sieved to retrieve small parts. Without wishingto be bound by theory, it is believed that the sintering reduction agentfunctions by scavenging oxygen from the atmosphere of the boronizingprocess. Preferably, the sintering reduction agent is selected fromcarbon black, graphite, activated carbon, charcoal, or mixtures thereof.More preferably, the sintering reduction agent is carbon black.Preferably, the sintering reduction agent is present in the powderboronizing composition in an amount of 10.0 to 30.0 wt %, based on thetotal weight of the powder boronizing composition. More preferably, thesintering reduction agent is present in the powder boronizingcomposition in an amount of 12.0 to 25.0 wt %. Most preferably, thesintering reduction agent is present in the powder boronizingcomposition in an amount of 18.0 to 22.0 wt %. Levels of sinteringreduction agent less than those recited can result in the boridingpowder pack becoming sintered into a solid block of caked powder that isextremely difficult to break apart and remove parts from afterprocessing. Levels of sintering reduction agent greater than thoserecited can result in the boriding powder having greatly reduced thermalconductivity making it take longer to heat and cool the boriding powderpacks. With lower thermal conductivity, it is difficult to uniformlyboride parts in larger size powder packs as the center portion of largepacks are much slower to heat and cool than the outside edges of thesame pack. The density of carbon black is also lower than the bulkpowder, and it has been observed that the iron-boride compound layersare not as compact and dense below the surface when excessive amounts ofcarbon black are used instead of filling with more dense diluentmaterials such as SiC powder. This is mainly due to a specific mass ofcarbon black occupying more volume than the same mass of SiC powder,thus making the same weight percentages of boron source and activatorbecome more dilutely spread out across a larger volume of powder.

Diluent

The diluent is included in the boronizing powder composition to providebulk to the composition. The diluent must have good heat conductivity,must not sinter together during the process, and have high densitymaking it more difficult for outside atmosphere gases to permeate intothe pack and also making it more difficult for the boriding vapors (BF₃,BCl₃) to quickly exit the pack, and preferably, should be inert to theactivator, boron source and sintering reduction agent. Preferably, thediluent is selected from SiC, alumina, zirconia or mixtures thereof.More preferably, the diluent is SiC. Preferably, the diluent is presentin the powder boronizing composition in an amount of 45.5 to 88.5 wt %,based on the total weight of the powder boronizing composition. Morepreferably, the diluent is present in the powder boronizing compositionin an amount of 61.0 to 82.5 wt %. Most preferably, the diluent ispresent in the powder boronizing composition in an amount of 69.0 to76.0 wt %. Levels of diluent less than those recited can result in theinclusion of active components at higher levels than are desirable froman economic standpoint. Levels of diluent less than those recited couldalso lead to dual-phase iron-boride compound layers if the boriding packbecomes too potent with not enough diluent present. Levels of diluentgreater than those recited can result in levels of active componentsthat are too low to provide adequate boride layer properties.

Boronizing Compositions

In one embodiment, the boronizing powder composition comprises: 0.5 to25.0 wt % of a boron source; 1.0 to 25.0 wt % of an activator; and 50.0to 98.5 wt % of a diluent, based on the total weight of the boronsource, activator and diluent. Preferably, the boronizing powdercomposition comprises 2.0 to 20.0 wt % of the boron source; 2.0 to 20.0wt % of the activator; and 60.0 to 96.0 wt % of the diluent, based onthe total weight of the boron source, activator and diluent. Morepreferably, the boronizing powder composition comprises 2.0 to 6.0 wt %of the boron source; 2.0 to 8.0 wt % of the activator; and 86.0 wt % to96.0 wt % of the diluent, based on the total weight of the boron source,activator and diluent.

In another embodiment, the boronizing powder composition comprises 0.5to 25.0 wt % of a boron source selected from B₄C, amorphous boron,calcium hexaboride, borax or mixtures thereof; 1.0 to 25.0 wt % of anactivator selected from KBF₄, ammonia chloride, cryolite, sodiumfluoride, ammonium bifluoride, potassium fluoride, calcium fluoride, ormixtures thereof; and 50.0 to 98.5 wt % of a sintering reduction agentselected from carbon black, graphite, activated carbon, charcoal ormixtures thereof, based on the total weight of the boron source,activator and sintering reduction agent.

In still another embodiment, a particularly effective powder boronizingcomposition of the present subject matter has been particularly designedto provide a boride layer of exceptionally high Fe₂B level, highhardness, low porosity with good thickness levels, as well as anexcellent uniformity of the boride layer. The boride layer also displaysexcellent resistance to cracking, flaking or oxidation in subsequentheat treatment steps as described below. Preferably, the powderboronizing composition contains: (a) 0.5 to 4.5 wt % of a boron sourceselected from B₄C, amorphous boron, calcium hexaboride, borax ormixtures thereof; (b) 45.5 to 88.5 wt % of a diluent selected from SiC,alumina, zirconia, or mixtures thereof; (c) 1.0 to 20.0 wt % of anactivator selected from KBF₄, ammonia chloride, cryolite, sodiumfluoride, ammonium bifluoride, potassium fluoride, calcium fluoride, ormixtures thereof; and (d) 10.0 to 30.0 wt % of a sintering reductionagent selected from carbon black, graphite, activated carbon or mixturesthereof. More preferably, the powder boronizing powder compositioncontains (a) 2.0 to 4.0 wt % of the boron source; (b) 61.0 to 82.5 wt %of the diluent; (c) 3.5 to 10.0 wt % of the activator; and (d) 12.0 to25.0 wt % of the sintering reduction agent. Even more preferably, thepowder boronizing compositions contains: (a) 2.0 to 3.0 wt % of theboron source; (b) 69.0 to 76.0 wt % of the diluent; (c) 4.0 to 6.0 wt %of the activator; and (d) 18.0 to 22.0 wt % of the sintering reductionagent.

In another embodiment, the boronizing powder composition comprises:boronizing powder composition comprises: 0.5 to 25.0 wt % of a boronsource selected from B₄C, amorphous boron, calcium hexaboride, borax ormixtures thereof; 1.0 to 25.0 wt % of an activator selected from KBF₄,ammonia chloride, cryolite, sodium fluoride, ammonium bifluoride,potassium fluoride, calcium fluoride, or mixtures thereof; and 50.0 to98.5 wt % of a diluent, based on the total weight of the boron source,activator and diluent.

In still another embodiment, the subject matter of the presentdisclosure relates to a boronizing powder composition comprising: 0.5 to3.0 wt % of a boron source selected from B₄C, amorphous boron, calciumhexaboride, borax or mixtures thereof; 1.0 to 15.0 wt % of an activatorselected from KBF₄, ammonia chloride, cryolite, sodium fluoride,ammonium bifluoride, potassium fluoride, calcium fluoride, or mixturesthereof; and 82.0 to 98.5 wt % of a stream selected from sinteringreduction agents, diluents or mixtures thereof, the sintering reductionagents being selected from carbon black, graphite, activated carbon,charcoal or mixtures thereof, and the diluents being selected from SiC,alumina, zirconia or mixtures thereof.

Preferably, the powder boronizing composition has a ratio of sinteringreduction agent/boron source, i.e., of component (d)/component (a) of2.2 to 60.0. More preferably the powder boronizing composition has aratio of component (d)/component (a) of 3.0 to 12.5. Even morepreferably, the powder boronizing composition has a ratio of component(d)/component (a) of 6.0 to 11.0.

Levels of the boron source less than those recited can result in apoorer quality boride layer due to thinner boride layers and larger gapsand spacing between the teeth in the boride layer that would be occupiedby lower hardness substrate material. The boride layer may also beinferior, because the surface structure is composed of both ferrite plussingle phase Fe₂B. Levels of the boron source greater than those recitedcan result in poorer boride layer quality due to formation of adual-phase boride layer comprised of both FeB and Fe₂B which hasinferior performance characteristics when compared to a single-phaseboride layer comprised of only Fe₂B iron boride. Levels of activatorless than those recited can result in sintering of the boronizingpowder, a highly porous boride layer, or a poorer quality boride layerdue to incomplete layers or the formation of voids and porosity in theboride layer. Levels of activator greater than those recited can alsoresult in sintering of the boronizing powder, as well as excessiveunnecessary quantities of spent reaction gas, which can presentenvironmental challenges. Levels of sintering reduction agent less thanthose recited can result in the boriding powder pack becoming sinteredinto a solid block of caked powder that is extremely difficult to breakapart and remove parts from after processing. Levels of sinteringreduction agent greater than those recited can result in shallowerboride layers and the boriding powder having greatly reduced thermalconductivity, making it take longer to heat and cool the boriding powderpacks. With lower thermal conductivity, it is more difficult touniformly boride parts in larger size powder packs as the center portionof large packs are much slower to heat and cool than the outside edgesof the same pack. The density of the sintering reduction agent is alsolower than the bulk powder, and it has been observed that theiron-boride compound layers are not as compact and dense below thesurface when excessive amounts of sintering reduction agent are usedinstead of filling with more dense diluent materials such as SiC powder.This is mainly due to a specific mass of the sintering reduction agentoccupying more volume than the same mass of SiC powder, thus making thesame weight percentages of boron source and activator become moredilutely spread out across a larger volume of powder. Levels of diluentless than those recited can result in the inclusion of active componentsat higher levels than are desirable from an economic standpoint. Levelsof diluent less than those recited could also lead to dual-phaseiron-boride compound layers if the boriding pack becomes too potent withnot enough diluent present. Levels of diluent greater than those recitedcan result in levels of active components that are too low to provideadequate boride layer properties.

Properties of Boronized Metals

The properties of the boride layer affected by the powder boronizingprocess include thickness, thickness variability, relativeconcentrations of Fe₂B and FeB, hardness and porosity. The thickness ofthe layer can vary depending on the boronizing powder composition, themetal being boronized, the length of time for the boronizing and thetemperature of the boronizing. The thickness of the boride layer istypically from 0.0005 to 0.020 inches. Preferably, the boride layer is0.002 to 0.015 inches. More preferably, the boride layer is 0.005 to0.015 inches. The thickness of the boride layer is calculated as themaximum distance from surface of the workpiece to the deepest tips ofthe boride layer observed in the cross-sectioned microstructure, wherethe boride layer depth is measured by examining a cross-section of atreated surface using an optical microscope.

The variability of the thickness of the boride layer is a measure of theconsistency of the boronizing process. Optimally, the variability shouldbe as low as possible, since the degree of protection the pipe enjoysfrom the boriding is dependent on its thickness, and portions of thepipe having a lower thickness are obviously less protected. For thepurpose of this specification, the variability of the thickness of thelayer is defined as the range of boride layer depth results observed inat least 5 randomly selected locations of the surfaces being examined,i.e., the distance in inches between the highest value and the lowestvalue. For example, if the analysis of five locations results in a layerthickness ranging from 0.008″ to 0.014″, the variability is thedifference between the highest and lowest values, 0.006″. The reportedthickness of the layer is the midpoint of that range, or 0.011″.Preferably, the variability of the thickness of the layer produced bythe process of the present subject matter is no greater than 0.005″.More preferably, the variability of the thickness of the layer is nogreater than 0.003″. However, in no event will the variability begreater than 50.0% of the boride layer thickness.

The formation of the boride layer can include two phases: Fe₂B and FeB.Of these two phases, Fe₂B is preferred because it is less brittle than aFeB phase and exists under a state of compressive residual stressinstead of tensile residual stress. Moreover, because the two phaseshave different coefficients of thermal expansion, mixtures of the twophases are subject to crack formation at the Fe₂B/FeB interface of adual-phase layer. The cracks can result in spalling or flaking, or evenfailure when subjected to mechanical stress. Thus, the percentage ofFe₂B in the borided layer should be as high as possible. Preferably, theboride layer comprises 90.0 to 100.0 vol % Fe₂B and 0 to 10.0 vol % FeB,where the fractions of Fe₂B and FeB are measured by comparing the depthof the Fe₂B boride layer teeth to the depth of the FeB boride layerteeth in the cross-sections examined; (e.g., if the total boride depthis 0.010″, with the Fe₂B depth being 0.008″ and the FeB depth being0.002″, then the boride layer would be said to contain 20 vol % of theFeB and 80 vol % of the Fe₂B, based on the total amount of the FeB andFe₂B). Such analysis is normally conducted using measurements of bothFeB and Fe₂B boride layer depths in a mounted and polished cross-sectionof the boride layer using an optical microscope with image analysismeasurement tools or a measuring reticle. More preferably, the boridelayer boride layer comprises 95.0 to 100.0 vol % Fe₂B and 0 to 5.0 vol %FeB. Even more preferably, the boride layer comprises 98.0 to 100.0 vol% Fe₂B and 0 to 2.0 vol % FeB. Most preferably, the boride layer shouldbe a single phase Fe₂B layer, where for the purpose of thisspecification, the term “single-phase Fe₂B layer” means the layercontains no FeB.

Porosity is also a measure of the quality of the boride layer wherebyvoids or discontinuities can exist in the layer. Inspection for porosityis performed by microscopic examination of a mounted and polishedcross-section of the boride layer. Preferably, the porosity of theboride layer should be less than 10%, where the porosity is measured byvisual estimate or image analysis of the boride layer microstructure.More preferably, the porosity of the boride layer should be less than5%.

Hardness of the boride layer can be measured according to the VickersHardness test, ASTM E384 where hardness measurements may be madedirectly on the treated surface or may be made on a mounted and polishedcross-section of the boride layer. Preferably, the hardness of theborided layer is from 1100 to 2900 HV. More preferably, the hardness ofthe borided layer in ferrous materials is from 1100 to 2000 HV.

Heat Treatment of Borided Pipe

It has been unexpectedly found possible to produce borided pipes fordeep well applications that comply with the associated stringentspecifications for L80 grade pipe according to the American PetroleumInstitute's, “Specification for Casing and Tubing,” API Specification5CT, Ninth Edition, July 2011, the disclosure of which is herebyincorporated by reference. This process involves austenitizing,quenching and tempering a pipe after it has been borided. Until now,borided pipe that meets any API 5CT grade with yield strengths and burstpressures higher than J55 grade has not been mass produced and madeavailable to oil producers. The boriding process involves heating pipeto an austenitizing temperature in order to form the boride layer, andboriding suppliers will typically remove the tubing from the furnace atthe boriding temperature, and air cool the pipe from the boridingtemperature down to ambient room temperature. This austenitizing thatoccurs during boriding followed by air cooling is a normalizing process,and the resultant core properties of the boronizing process willtypically be 55-60 ksi yield strength which will marginally meet the API5CT J55 grade requirements of 55-80 ksi yield strength.

Preferably, the borided pipe is emptied of borided powder and cooledprior to further treating to achieve a higher L80 grade yield strengthrequirement of 80-95 ksi yield strength, requiring rapid liquidquenching of the pipes from the boriding temperature followed bytempering in order to transform the austenite structure present at theboriding temperature to a martensite core structure, as described below.Attempting to quench pipes filled with boriding powders couldcontaminate the liquid quenching bath if liquids come into contact withthe boriding powder. If the boriding powder were to mix with quenchantsit would also turn the boriding powder into a messy sludge or slurrythat couldn't be dried and re-used again and it would be difficult toproperly clean the boriding media out of the tubing after the process.Another potential pitfall of full-body quenching the tubes with powderstill present in them is that the tubes may distort and warp if notcooled uniformly, resulting in severe warpage and bending that wouldthen require post-boride straightening with high deflections which couldthen crack the boride layers. If pipes are removed from the boridingfurnace at the end of the boriding cycle and are not individuallyquenched with uniform agitation from all angles, such as quenchingmultiple pipes at once together or quenching pipes resting on a supportor pipe holding device that can retain heat, they can coolnon-uniformly, causing one side of the pipe to contract more rapidlythan the other side of the pipe during cooling and cause the entire pipeto become badly bowed. Pipe straightening is typically required for longpieces of pipe after such high temperature heating because the pipingtends to bow or sag along its length. It is critically important to keepthese pipes as straight as possible during boriding and hardening suchthat either no straightening or straightening with only minimaldeflections is required in order to prevent and minimize any cracking ofthe boride layer. A new processing scheme has been developed where pipesare stress relieved and optionally straightened prior to boriding inorder to create a stress-free tube that is straight prior to boriding,the pipes are then fixtured onto heat resistant supports in such amanner that it will prevent them from sagging or creep-distorting duringthe high temperature boriding cycle, the pipes are then borided onstraight fixtures and then cooled to ambient. After all spent boridingpowder is removed, the borided pipes can be straightened prior tohardening with minimal deflections required, such that the boride layerwill not crack or spall off during straightening. In order to harden thepipes using a quench and temper type of heat treatment, the pipes areinduction hardened, quenched and tempered. Induction hardening andtempering of individual pipes with uniform heating and cooling ratesallows for pipe surfaces to be quickly heated to an austenitizingtemperature in a manner of just minutes. The short heating time allowsfor the process to be performed in air atmosphere without any excessivescaling or oxidation of the boride layer surface or oxidation ofuntreated pipe surfaces. The induction hardening process is alsoperformed on individual tubes passing on cross-rollers through inductioncoils such that the tubes are spinning on a straight track of rollersthat helps maintain pipe straightness along with performing uniformheating as the rotating pipe is passed through heating coils. After thepipe has passed through all the induction heating coils, it has reachedthe desired austenitizing temperature and the core material hascompletely transformed to austenite. The austenitic heated pipe thenpasses on rollers as it is rotating through a quenching coil or quenchnozzles that direct liquid quenchant, typically water or polymer, fromall radial angles onto the pipe surface such that the pipe is uniformlyquenched radially and maintains acceptable limits of straightness duringthe heating and quenching steps. After quenching, the pipe will passthrough another set of induction heating coils that heats the tubing toa desired tempering temperature. If performed correctly, the pipes maystill meet the requirements for straightness after induction hardeningand tempering and may not need any additional straightening operationsto be performed which further mitigates any risk of cracking the boridelayer by avoiding an additional straightening operation. Differentgrades of API 5CT tubing can be met by altering the temperingtemperature to produce a specific set of tensile and yield strengthproperties. The induction hardening and tempering process after boridingenables treatment of borided pipes to reach the required specificationsfor L80 and other grades of API 5CT pipe, without oxidation, cracking orflaking of the boride layer after pipe straightening. Suchspecifications for API 5CT Grade L80 include, e.g., a KSI yield strength(80-95 KSI); KSI minimum tensile strength (95 KSI); and HRC maximumhardness (23 HRC). This is possible because the induction hardeningprocess allows for reheating, quenching and tempering of a borided partwith minimal times at heat where oxidation is not a concern and creepdistortion is minimal along with induction hardening allowing foruniform radial heating and cooling to prevent pipes from bowing ordistorting during heating or quenching due to uneven heat distribution.

Induction hardening is one option for post-boride treatment that ispossible. Another option for austenitizing, quenching and temperingafter boriding would be furnace hardening. Furnace hardening is alsopossible and may be performed in lieu of induction hardening. The maindifference is a longer exposure time to heat is required to soak thepipes out and fully austentize the material. The longer heat exposuretimes will usually necessitate the use of heating pipe in an inertatmosphere, such as nitrogen, argon, helium, endothermic gas, exothermicgas or similar, to prevent oxidation of borided and unborided pipesurfaces. The longer heat exposure also allows more time for pipes tosag and warp out of straight if not properly supported during the entirecycle and typically a walking beam or tube processing furnace will beused where pipes are rotating during heating and supported over theirentire length. After the pipes are fully austentized, they may beremoved from the furnace and liquid quenched in water, salt, oil, brineor polymer to transform the core material to martensite similar to theinduction hardening process followed by tempering at differenttemperatures in order to meet various different API 5CT graderequirements for tensile strength, yield strength, and hardness.

While L80 is the most popular choice for grade, the treatment of theborided pipes, can be alternatively adjusted to meet the requirements ofother desirable high strength rated piping such as C90, T95, C110, P110,Q125, N80, and R95 grades by adjusting the tempering temperature afterquenching.

Pipes produced by the process of the present subject matter have boridelayers that are physically uniform. For the purposes of thisspecification, the term “physically uniform” when applied to boridelayers produced by the described process to harden borided pipes meansthat the boride layers are not oxidized, cracked or flaked. An internalborescope may be used to inspect tubing bores after all processes arecomplete to ensure no visible cracking or spalled areas are present.

Heating Step

The first step of the treatment is a heating step where the pipe isaustenitized, i.e., where the pipe is heated above its criticalaustenitizing temperature for a time period long enough for the metal tobe transformed into an austenite structure. The heating can either be aninduction heating step or a furnace heating step. Preferably, theheating is an induction heating step. Austenite is an intermediatecrystal structure that is stable at high temperatures in steel and iscapable of transforming into different crystal structures during laterprocessing or heat treatment depending on cooling rates and schedules toa variety of different microstructures that may be desired. The requiredtemperature for heating is preferably from 1400 to 2000° F. Morepreferably, the temperature is from 1400 to 1900° F., and even morepreferably from 1500 to 1800° F. Preferably, the heating is conductedusing induction heating coils in an induction machine using airatmosphere. Alternative, the heating may be performed in hightemperature furnaces using a protective inert atmosphere.

Quenching Step

Following the heating step is a quenching step. In the quenching step,the metal is cooled from the temperatures of the heating step, andbecomes hardened as the austenite is transformed into martensite. Thequenching is preferably performed with water, oil, polymer, brine, saltor combinations thereof. Preferably, the quenching media is at atemperature that may range from 40 to 200° F. The quenched metal pipe isreduced to a temperature range of 40 to 200° F. during immersion intothe quenchant and then allowed to cool to ambient room temperaturebefore tempering

Tempering Step

Following the quenching step is a tempering step. In the tempering step,the pipe is reheated from the quenched temperature or ambient to reducethe hardness and strength to the desirable level while increasing thetoughness and ductility of the hardened steel, while removing thetensions in the structure to improve ductility, leaving the steel withthe required hardness and strength levels. The tempering temperature ispreferably from 250 to 1375° F., more preferably, from 1250 to 1375° F.,and even more preferably, from 1300 to 1375° F. for L80 grade. Thetempering step can be conducted either by induction heating or furnaceheating. Preferably, the tempering step is conducted by inductionheating.

In each of the furnace heating, quenching, and tempering steps, aprotective atmosphere, such as vacuum, neutral salt, nitrogen, argon,helium, endothermic gas, or exothermic gas, can optionally be used forprotection of the boride layer that does not cause any oxidation,degradation or reaction of the boride layer during heating. In inductionheating, the atmosphere surrounding the tubing during all steps may beair atmosphere due to the short time exposures required that istypically less than a minute.

Preferably, the tempered pipe produced in the tempering step isnon-threaded. Threading the ends of the pipes facilitates connecting thepipe to adjacent pieces of pipe, eventually forming a series ofconnected pieces of pipe that constitutes the well pipe. Threading thepipe after boronizing and heat treating in this manner advantageouslyavoids distorting the grooves of the threads during the heating and thecooling steps. Threads are also prone to damage as they can be easilynicked, dinged and damaged during installation of end caps, removal ofend caps, handling and transport of the pipes and subsequent cleaningand straightening operations after boriding and/or hardening andtempering. In either of these situations the pipe would either have tobe mechanically modified in an additional step or discarded as therewould be a risk of thread leakage or poor quality connections due topoor quality threads. Thus, it is advantageous to boride and hardenunthreaded tubing and then perform the threading after all of the otheroperations which could compromise the thread integrity have beencompleted.

The heating, quenching and tempering steps can alternately be conductedwhen boriding powder has not been removed from the pipe, following theboronizing step. Preferably, the powder is removed prior to the heating,quenching and tempering steps.

The treated, borided steel produced by the treatment step according tothe present subject matter meets the specification of API 5CTspecification L-80.

The boronized pipes produced according to the present subject matter areespecially useful in processes of the oil producing industry where thepipes are employed in deep wells. Preferably, the boronized pipes areused in a process wherein a sucker rod pump is employed within the pipe.The boronized pipes produced according to the present subject matter areespecially useful in the oil and gas, refining, concrete, mining andchemical industries where the pipes are used to transport abrasiveslurries within the pipe.

Referring now to FIG. 1, shown is a loading and unloading process forfilling and emptying boronizing powder from metal tubes. A hydraulicpowered tilting station (1) has pipes to be boronized (2) loaded on thebed. Prior to lifting, a bottom end cap (3) is fitted to the lower endof the tube. The pipe is tilted up into the air and positionedunderneath a powder conveyance system (4) that uses either pneumaticconveyance, screw conveyor, rotary valve feeder, loss in weight feederor any combination thereof to pull boronizing powder out of a storagecontainer (5) and into the pipe to be boronized (2). A vibration unit(6) will be attached to either the tubes or the tilting station (1) andwill vibrate the tubes during loading to facilitate with settling ofpowder to ensure tubes are completely filled and powder is packedtightly in the interior bore of the tube. After the tubes are filled,the top end cap (7) is installed on the top of the tube to seal powderinside the tube. The tubes are then lowered back to horizontal afterfilling and transferred to the racking station for boronizing. Afterboronizing, the boronized tubes (8) are loaded back onto the tiltingstation (1) and tilted upwards placed above a spent boronizing powdercollection container (9) and the bottom end cap (3) is removed. Thetubes are vibrated during emptying using a vibration device (6) attachedto either the tubes directly or the tilting station. After all powderhas emptied out of each tube, the tubes are tilted back down tohorizontal, the top end cap (7) is removed and the finished tubes aremoved out of the processing area. Filling and unloading of the powder isconducted in a closed system with venting to baghouse or cyclones aswell.

Referring now to FIG. 2, shown is a pipe with a flared end and asplit-bushing end cap composed of an end cap portion and a split-bushingportion. The interior surface of the cylindrical portion of the end capportion is threaded and the other end is sealed. The split-bushingportion is shown as being in 2 curved sections, where the curvedsections at one end are fitted with a solid flange portion

Referring now to FIG. 3, shown is a split-bushing end cap for anunthreaded flared tube being mounted on flared section of tube where thesplit bushing diameter fits around the main body of the tube but willnot be able to slip over the larger diameter of the flared end of thepipe.

Referring now to FIG. 4, shown is the installation of a split-bushingendcap for boronizing unthreaded tubes with the two split bushing piecessurrounding the main body diameter of the pipe. The two split bushingpieces are about to be screwed into the end cap where the split bushingswill be pulled up into the end cap during until inner diameter of thesplit bushings catches on the tapered section of the larger flared enddiameter and secures the end cap and split bushing assembly tightagainst the end of the pipe.

Referring now to FIG. 5, shown is a split-bushing endcap installed onthe end of a flared tube.

Referring now to FIG. 6, shown is a split-bushing along with thehexagonal flange from a variety of angles.

Referring now to FIG. 7, shown is an end cap for use along with thesplit-bushing from a variety of angles.

Referring now to FIG. 8, shown is a plate end cap.

The following Examples further detail and explain the preparation andperformance of the powder boronizing compositions. Those skilled in theart will recognize many variations that are within the spirit of theinvention and scope of the claims.

EXAMPLES Example 1

Borided, hardened and tempered tubing meeting the requirements of API5CT Grade L80 2⅞″ tubing has been produced using the following method.Tubing was initially stress relieved at 900 F in order to remove anyresidual stresses present from the tube making process prior to boridingsuch that the tubing should not warp upon heating during boriding asresidual stresses are relieved. After stress relieving, the tubing isinspected for straightness and straightened to a total indicated runout(TIR) of 0.2% of the pipe length prior to boriding. Boriding powder ofcomposition 71% SiC, 3% B₄C, 5% KBF₄, 20% Carbon Black was charged intothe tubing and endcaps were secured onto both ends of the tubing to sealthe boriding powder inside the tube. Tubing was then fixtured to heatresistant supports that will help maintain straightness during boridingand prevent any creep distortion or bending due to non-uniformheating/cooling and placed into the boriding furnace. Tubes were thenheated to 1750 F for 8 hours, slow cooled in the furnace and removedfrom the boriding furnace. The boriding powder was removed from thetubes after boriding. Straightening was then performed where tubing wasstraightened to meet a TIR less than 0.1% of tube length prior topost-boride hardening. Post-boride hardening consisted of heating theborided tubing using an induction machine to a temperature of 1750 F forthe austenitizing step, water quenching to ambient temperature and thentempering at 1320 F using an induction tempering machine. Both theaustenitizing and tempering times for any point along the tubing wasless than 5 minutes. After hardening and tempering, the pipes wereinspected for straightness and were all found to meet API 5CTrequirements for total indicated runout and did not requirestraightening after induction hardening. After boriding, hardening andtempering, the tubing was inspected for core mechanical properties whichwere observed to be 103.5 ksi tensile strength, 93.7 ksi yield strength,and 15.8-18.3 HRC hardness. Microstructure was also inspected and theboride layer was observed to be physically uniform and free of anyoxidation, cracks and spalling. The boride layer depth was measured tobe 0.008″ total depth with 20% FeB present. The boride layer hardnessmeasured 1500-1800 HV. The boride layer had no porosity or voidsobserved. The inside bores of the tube were inspected using a borescopeand no visual signs of boride layer cracking or spalled areas wereobserved. All requirements for API 5CT Grade 80 were met along withhaving a physically uniform 0.008″ deep boride layer containing 20% FeB.

Examples 2-10

A series of boriding powder compositions were prepared to evaluatesintering performance and evaluation of the boriding layer deposited.The compositions included a boron source (B₄C), activator (KBF₄),sintering reduction agent (carbon black), and diluent (silicon carbide).The level of boron source was varied, while maintaining the activatorand carbon black levels constant. Pieces of precision ground AISI 1018steel (⅛″ thick×½″ long) were cut from a single bar all having the samesteel chemistry. Each bar was notched on the end of bar to identify it.Each of the boriding powder compositions was then placed inside a smallsealed pipe constructed from a standard black iron threaded pipe nipple(¾″ pipe size×4″ long) with two ¾″ cast iron threaded pipe caps screwedonto both ends. The steel test bars were suspended in the center of thesealed pipes completely submerged in the boriding powder composition.All the sealed capped pipes holding the test bars suspended in powderinside the capped pipes were placed inside a large container and loadedinto a furnace. The furnace was ramped up to heat at 500° F. per hour to1750° F. and held at 1750° F. for 12 hours at heat followed by slowcooling. The atmosphere in the furnace was air. At the end of theboriding, each pipe was opened and its contents removed. The powder wasexamined for evidence of sintering, and each test bar was sectioned,mounted, ground and polished. The cross-sections were then etched with a2% nital acid solution to reveal the boride layer microstructure presentin the cross-section. The boride layer microstructures were photographedand the boride layer analyzed. The boriding compositions and results areshown in Table 1.

TABLE 1 Example 2 3 4 5 6 7 8 9 10 B₄C, wt % 0.3 0.5 1.0 2.0 2.5 3.0 4.04.5 5.0 KBF₄, wt % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Carbon 20.0 20.020.0 20.0 20.0 20.0 20.0 20.0 20.0 Black, wt % Silicon 74.7 74.5 74.073.0 72.5 72.0 71.0 70.5 70.0 Carbide, wt % Sintering no no no no no nono no no Boride Layer 0.004 0.004 0.005 0.0075 0.008 0.008 0.010 0.0090.010 Thickness, inch Boride Layer (1) (1) (1) (2) (2) (2) (2) (2) (3)Quality* *(1) incomplete layer at surface (2) single-phase Fe₂B solidlayer (3) mostly single-phase Fe₂B solid layer, some FeB at surface (4)highly porous and incomplete layer

For the purposes of this specification, the term “incomplete layer atsurface” means the presence of iron-boride compound, but not acontinuous layer. This surface structure is ferrite which is a steelstructure where there is not any iron-boride layer precipitating outright at the surface of the part. The term “shallow or shallower” boridelayer means that the layer is not as deep, and refers to how deep belowthe surface of the borided part where an iron-boride compound ispresent. The term “highly porous and incomplete layer” means layers withempty pores (voids) present in the boride layer that have poormechanical properties. It's just literally bubbles of gas or vacuumbeneath the surface that form when we don't have enough KBF₄ present.The term “single-phase Fe₂B solid layer,” means a complete layer havinga single phase of Fe₂B with no FeB or ferrite present.

The results of Table 1 indicate that none of the Examples exhibitedsintering. Samples 2-4, corresponding to boron source concentrations 0.3to 1.0 wt % exhibit incomplete boride layers at the surface. Samples5-9, corresponding to boron source concentrations of 2.0 to 4.5 wt %exhibit a solid, single-phase layer of Fe₂B. Sample 10, corresponding toa boron source concentration of 5.0 wt %, produces a boride layer havinga mostly single-phase Fe₂B solid layer, with some FeB at the surface.

Examples 11-18

A series of boriding powder compositions were prepared and tested aswith Examples 2-10 above. The boriding compositions and results areshown in Table 2, where the activator KBF₄ is varied between 0.5 to 25.0wt %, while the boron source and carbon black concentrations are heldconstant.

TABLE 2 Example 11 12 13 14 15 16 17 18 B₄C, wt % 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 KBF₄, wt % 0.5 1.0 3.5 4.0 6.0 10.0 20.0 25.0 Carbon 20.020.0 20.0 20.0 20.0 20.0 20.0 20.0 Black, wt % Silicon 77.0 76.5 74.073.5 71.5 67.5 57.5 52.5 Carbide, wt % Sintering yes yes no no no no noyes Boride 0.004 0.006 0.008 0.008 0.010 0.010 0.010 0.010 LayerThickness, inch Boride (4) (4) (2) (2) (2) (2) (2) (2) Layer Quality**(1) incomplete layer at surface (2) single-phase Fe₂B solid layer (3)mostly single-phase Fe₂B solid layer, some FeB at surface (4) highlyporous and incomplete layerThe results of Table 2 indicate that samples having the lowest levels ofactivator (Examples 11 and 12 with activator levels of 0.5 and 1.0 wt %,respectively), and at the highest level of activator (Example 18,activator level of 25.0 wt %) exhibit sintering. Examples 11 and 12 alsoexhibit highly porous and incomplete boride layers, with the rest of thesamples having single-phase Fe₂B solid layers.

Examples 19-26

A series of boriding powder compositions were prepared and tested aswith Examples 2-10 above. The boriding compositions and results areshown in Table 3, where the sintering reduction agent (carbon black) isvaried between 5.0 to 35.0 wt %, while the boron source and activatorconcentrations are held constant.

TABLE 3 Example 19 20 21 22 23 24 25 26 B₄C, wt % 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 KBF₄, wt % 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Carbon 5.0 10.012.0 18.0 22.0 25.0 30.0 35.0 Black, wt % Silicon 87.5 82.5 80.5 74.570.5 67.5 62.5 57.5 Carbide, wt % Sintering yes no no no no no no noBoride 0.010 0.010 0.010 0.009 0.010 0.006 0.006 0.005 Layer Thickness,inch Boride (2) (2) (2) (2) (2) (2) (2) (2) Layer Quality* *(1)incomplete at surface (2) single-phase Fe₂B solid layer (3) mostlysingle-phase Fe₂B solid layer, some FeB at surface (4) highly porous andincomplete layer

The results of Table 3 indicate that Example 19, containing the lowestlevel of sintering reduction agent (5.0 wt %) results in sintering. Allof the samples provided boride layers having single-phase, Fe₂B layers.However, Examples 24-26, corresponding to levels of anti-sintering agentof 25.0 to 35.0 wt % result in lower boride layer thickness. Withoutwishing to be bound by theory, Applicants believe that one possibleexplanation is that the lower thermal conductivity (higher carbon blackcontent) powders took a longer time to reach the 1750° F. boridingtemperature during the test, and started boriding later than the lowercarbon black concentration examples. Another possible explanation isthat the low density of the carbon black causes a fixed mass of carbonto take up significantly more volume than silicon carbide, and that thisresulted in diluting the boron carbide and KBF₄ concentrations.

Other features, advantages and embodiments of the invention disclosedherein will be readily apparent to those exercising ordinary skill afterreading the foregoing disclosure. In this regard, while specificembodiments of the invention have been described in considerable detail,variations and modifications of these embodiments can be effectedwithout departing from the spirit and scope of the invention asdescribed and claimed.

We claim:
 1. A process comprising: placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to form aborided layer on the inside surface, and spent boronizing powder;removing the spent boronizing powder from the pipe, thereby forming anempty boronized pipe; heating the boronized pipe to above itsaustenitizing temperature, thereby forming an austenitized pipe;quenching the austenitized pipe, thereby forming a quenched pipe; andtempering the quenched pipe, thereby forming a tempered pipe.
 2. Theprocess of claim 1 wherein the borided layer comprises 80.0 to 100.0 vol% Fe₂B and 0 to 20.0 vol % FeB, based on the total amount of the Fe₂Band FeB.
 3. The process of claim 1 wherein the heating to form theaustenitized pipe is an induction heating.
 4. The process of claim 1wherein the heating to form the austenitized pipe is a furnace heating.5. The process of claim 1 wherein the tempered pipe meets the mechanicalproperty requirements for yield strength and tensile strength of API 5CTspecification Grade L80.
 6. The process of claim 1 wherein the boridedlayer is physically uniform.
 7. The process of claim 1 wherein theheating to form the austenitized pipe is from 1400 to 2000° F.
 8. Theprocess of claim 1 wherein the austenitized pipe is quenched to atemperature of 40 to 200° F.
 9. The process of claim 1 wherein thequenched pipe is tempered at a temperature from 250 to 1375° F.
 10. Theprocess of claim 1 wherein the quenching is conducted with water, oil,brine, polymer, salt or mixtures thereof.
 11. The process of claim 1wherein the tempering is induction tempering.
 12. The process of claim 1wherein the tempering is furnace tempering.
 13. The process of claim 1where the boride layer of the tempered pipe is physically uniform.
 14. Apipe produced by the process of claim
 1. 15. A boronized pipe that hasbeen hardened and tempered after boriding to meet mechanical propertiesof 80 ksi minimum yield strength and 95 minimum ksi tensile strength.16. The boronized pipe of claim 15 comprising a borided layer Fe₂Bcontent of 80.0 to 100.0 vol % and a borided layer FeB content of 0 to20.0 vol %, based on the total amount of the borided layer.
 17. Theboronized pipe of claim 16 wherein the borided layer Fe₂B content is95.0 to 100.0 vol % and the FeB content is 0 to 5.0 vol %, based on thetotal amount of the borided layer.
 18. The boronized pipe of claim 16wherein the borided layer is physically uniform.
 19. A process fortreating a boronized pipe comprising a borided layer on its interiorsurface, the process comprising: heating the boronized pipe to above itsaustenitizing temperature, thereby forming an austenitized pipe;quenching the austenitized pipe, thereby forming a quenched pipe; andtempering the quenched pipe, thereby forming a tempered pipe.
 20. Theprocess of claim 19 wherein the borided layer comprises 80.0 to 100.0vol % Fe₂B and 0 to 20.0 vol % FeB, based on the total amount of theborided layer.
 21. The process of claim 20 wherein the Fe₂B content ofthe borided layer is from 95.0 to 100.0 vol % and the FeB content of theborided layer is 0 to 5.0 vol %, based on the total amount of theborided layer.
 22. The process of claim 19 wherein the tempered pipemeets the mechanical property requirements for tensile strength andyield strength per API 5CT specification Grade L80.
 23. The process ofclaim 19 wherein the borided layer is physically uniform.
 24. A pipeproduced by the process of claim
 19. 25. A process comprising heating aboronized pipe comprising a borided layer on the pipe's interiorsurface, to above its austenitizing temperature, thereby forming anaustenitized pipe; and quenching the austenitized pipe, thereby forminga quenched pipe
 26. The process of claim 25 wherein the borided layercomprises 80.0 to 100.0 vol % Fe₂B and 0 to 20.0 vol % FeB, based on thetotal amount of Fe₂B and FeB.
 27. The process of claim 26 wherein theFe₂B content of the borided layer is from 95.0 to 100.0 vol % and theFeB layer is from 0 to 5 vol %, based on the total amount of Fe₂B andFeB.
 28. The process of claim 25 wherein the borided layer is physicallyuniform.
 29. A pipe produced by the process of claim
 25. 30. The processof claim 1 wherein the thickness of the borided layer is from 0.0005 to0.020 inches.
 31. The process of claim 30 wherein the thickness of theborided layer is from 0.002 to 0.015 inches.
 32. The process of claim 1wherein the boronizing powder composition comprises: 0.5 to 25.0 wt % ofa boron source selected from B₄C, amorphous boron, calcium hexaboride,borax or mixtures thereof; 1.0 to 25.0 wt % of an activator selectedfrom KBF₄, ammonia chloride, cryolite, sodium fluoride, ammoniumbifluoride, potassium fluoride, calcium fluoride, or mixtures thereof;and 50.0 to 98.5 wt % of a diluent selected from SiC, alumina, zirconia,or mixtures thereof, based on the total weight of the boron source,activator and diluent.
 33. The process of claim 1 wherein the boronizingpowder composition comprises 0.5 to 25.0 wt % of a boron source selectedfrom B₄C, amorphous boron, calcium hexaboride, borax or mixturesthereof; 1.0 to 25.0 wt % of an activator selected from KBF₄, ammoniachloride, cryolite, sodium fluoride, ammonium bifluoride, potassiumfluoride, calcium fluoride, or mixtures thereof; and 50.0 to 98.5 wt %of a sintering reduction agent selected from carbon black, graphite,activated carbon, charcoal, or mixtures thereof, based on the totalweight of the boron source, activator and sintering reduction agent. 34.The process of claim 1 wherein the boronizing powder compositioncomprises 0.5 to 4.5 wt % of a boron source selected from B₄C, amorphousboron, calcium hexaboride, borax or mixtures thereof; 45.5 to 88.5 wt %of a diluent selected from SiC, alumina, zirconia or mixtures thereof;1.0 to 20.0 wt % of an activator selected from KBF₄, ammonia chloride,cryolite, sodium fluoride, ammonium bifluoride, potassium fluoride,calcium fluoride, or mixtures thereof; and 10.0 to 30.0 wt % of asintering reduction agent selected from carbon black, graphite,activated carbon, charcoal or mixtures thereof.
 35. The process of claim1 wherein the boronizing powder composition comprises 0.5 to 3.0 wt % ofa boron source selected from B₄C, amorphous boron, calcium hexaboride,borax or mixtures thereof; 82.0 to 98.5 wt % of a stream selected fromdiluents and sintering reduction agents, the diluents being selectedfrom SiC, alumina, zirconia or mixtures thereof, and the sinteringreduction agent being selected from carbon black, graphite, activatedcarbon, charcoal or mixtures thereof; and 1.0 to 15.0 wt % of anactivator selected from KBF₄, ammonia chloride, cryolite, sodiumfluoride, ammonium bifluoride, potassium fluoride, calcium fluoride, ormixtures thereof.
 36. A process comprising: placing a boronizing powdercomposition in a metal pipe comprising a first end, a second end, aninside surface and an outside surface; heating the pipe to a boronizingtemperature, thereby forming a borided layer on the inside surface, andspent boronizing powder; and removing the spent boronizing powder fromthe pipe; wherein the spent boronizing powder is removed from the metalpipe with a closed transport system.
 37. The process of claim 36 whereinthe closed transport system is selected from pneumatic conveyance, screwconveyer, or combinations thereof.
 38. The process of claim 1 whereinthe removed spent boronizing powder is further treated with screens,sieves or by air classification, thereby forming a treated boronizingpowder stream.
 39. The process of claim 1 wherein the removed spentboronizing powder is treated by adding an additive component, therebyforming a first recycle stream.
 40. The process of claim 38 wherein thetreated boronizing powder stream is treated by adding an additivecomponent, thereby forming a second recycle stream.
 41. The process ofclaim 39 wherein the additive component is selected from a secondboronizing powder composition, a boron source, a sintering reductionagent, an activator, a diluent or mixtures thereof.
 42. The process ofclaim 40 wherein the additive component is selected from a secondboronizing powder composition, a boron source, a sintering reductionagent, an activator, a diluent or mixtures thereof.
 43. The process ofclaim 39 wherein the first recycle stream is recycled to a powderboronizing process.
 44. The process of claim 40 wherein the secondrecycle stream is recycled to a powder boronizing process.
 45. Theprocess of claim 36 wherein the boronizing powder composition comprises:0.5 to 25.0 wt % of a boron source selected from B₄C, amorphous boron,calcium hexaboride, borax or mixtures thereof; 1.0 to 25.0 wt % of anactivator selected from KBF₄, ammonia chloride, cryolite, sodiumfluoride, ammonium bifluoride, potassium fluoride, calcium fluoride, ormixtures thereof; and 50.0 to 98.5 wt % of a diluent, based on the totalweight of the boron source, activator and diluent.
 46. The process ofclaim 45 wherein the boronizing powder composition comprises: 2.0 to20.0 wt % of the boron source; 2.0 to 20.0 wt % of the activatorselected from KBF₄, ammonia chloride, cryolite, sodium fluoride,ammonium bifluoride, potassium fluoride, calcium fluoride, or mixturesthereof; and 60.0 to 96.0 wt % of the diluent selected from SiC,alumina, zirconia, or mixtures thereof; based on the total weight of theboron source, activator and diluent.
 47. The process of claim 46 whereinthe boronizing powder composition comprises 2.0 to 6.0 wt % of the boronsource; 2.0 to 8.0 wt % of the activator; and 86.0 wt % to 96.0 wt % ofthe diluent, based on the total weight of the boron source, activatorand diluent.
 48. The process of claim 36 wherein the boronizing powdercomposition comprises 0.5 to 25.0 wt % of a boron source selected fromB₄C, amorphous boron, calcium hexaboride, borax or mixtures thereof; 1.0to 25.0 wt % of an activator selected from KBF₄, ammonia chloride,cryolite, sodium fluoride, ammonium bifluoride, potassium fluoride,calcium fluoride, or mixtures thereof; and 50.0 to 98.5 wt % of ansintering reduction agent selected from carbon black, graphite ormixtures thereof, based on the total weight of the boron source,activator and sintering reduction agent.
 49. The process of claim 48wherein the boronizing powder composition comprises 2.0 to 20.0 wt % ofthe boron source; 2.0 to 20.0 wt % of the activator and 60.0 to 96.0 wt% of the sintering reduction agent, based on the total weight of theboron source, activator and sintering reduction agent.
 50. The processof claim 49 wherein the boronizing powder composition comprises 2.0 to6.0 wt % of the boron source; 2.0 to 8.0 wt % of the activator and 86.0to 96.0 wt % of the sintering reduction agent, based on the sinteringreduction agent.
 51. The process of claim 36 wherein the boronizingpowder composition comprises 0.5 to 4.5 wt % of a boron source selectedfrom B₄C, amorphous boron, calcium hexaboride, borax or mixturesthereof; (b) 45.5 to 88.5 wt % of a diluent selected from SiC, alumina,zirconia, or mixtures thereof; (c) 1.0 to 20.0 wt % of an activatorselected from KBF₄, ammonia chloride, cryolite, sodium fluoride,ammonium bifluoride, potassium fluoride, calcium fluoride, or mixturesthereof; and (d) 10.0 to 30.0 wt % of a sintering reduction agentselected from carbon black, graphite, activated carbon or mixturesthereof.
 52. The process of claim 36 wherein the borided layer has athickness from 0.0005 to 0.020 inches.
 53. The process of claim 52wherein the thickness of the borided layer is from 0.002 to 0.015inches.
 54. The process of claim 36 wherein the borided layer comprises80.0 to 100.0 vol % Fe₂B and 0 to 20.0 vol % FeB, based on the totalamount of Fe₂B and FeB.
 55. The process of claim 54 wherein the boridedlayer comprises 95.0 to 100.0 vol % Fe₂B and 0 to 5.0 vol % FeB, basedon the total amount of Fe₂B and FeB.
 56. A process comprising: placing aboronizing powder composition in a metal pipe comprising a first end, asecond end, an inside surface and an outside surface; heating the pipeto a boriding temperature, thereby forming a borided layer on the insidesurface, and spent boriding powder; and removing the spent boridingpowder from the pipe, wherein the boronizing powder is placed in themetal pipe by conveying the powder to the pipe using a closed transportsystem selected from pneumatic conveying, rotary valve, screw conveyeror combinations thereof.
 57. The process of claim 56 wherein the powderis conveyed by pneumatic conveying.
 58. The process of claim 56 whereinthe powder is conveyed by rotary valve.
 59. The process of claim 56wherein the powder is conveyed by screw conveyer.
 60. A processcomprising: placing a boronizing powder composition in a metal pipecomprising a first end, a second end, an inside surface and an outsidesurface; heating the pipe to a boriding temperature, thereby forming aborided layer on the inside surface, and spent boriding powder; andremoving the spent boriding powder from the pipe; wherein the boronizingpowder is placed in the metal pipe by conveying the powder to the pipeusing a closed transport system, and the spent boronizing powder isremoved from the metal pipe by a closed transport system.
 61. The metalpipe of claim 14 wherein the metal is selected from plain carbon steel,alloy steel, tool steel, stainless steel, nickel-based alloys,cobalt-based alloys, cast iron, ductile iron, molybdenum, or stellite.62. A process comprising transporting oil or gas in an oil well with thepipe of claim
 15. 63. A process comprising transporting oil or gas in anoil well with the pipe of claim
 24. 64. A process comprising: placing aboronizing powder composition in a metal pipe comprising a first end, asecond end, an inside surface and an outside surface; heating the pipeto form a borided layer on the inside surface, and spent boronizingpowder; removing the spent boronizing powder from the pipe, therebyforming an empty boronized pipe; heating the empty boronized pipe toabove its austenitizing temperature, thereby forming an austenitizedpipe; quenching the austenitized pipe, thereby forming a quenched pipe;tempering the quenched pipe, thereby forming a tempered pipe; andthreading the tempered pipe.
 65. A process comprising: boronizing anunthreaded pipe, thereby forming an unthreaded boronized pipe; andthreading the unthreaded boronized pipe.
 66. A pipe made by the processof claim
 64. 67. A pipe made by the process of claim
 65. 68. A processfor boronizing a metal pipe comprising a flared first end, a second end,an inside surface and an outside surface, the process comprising:fastening a first split-bushing end cap on the flared first end;depositing boronizing powder in the pipe; fastening a plate or secondsplit bushing end cap on the second end; and heating the pipe to atemperature from 1400° F. to 1900° F., thereby forming a borided layeron the inside surface, and generating spent reaction gases and spentboriding powder.
 69. The process of claim 68 wherein the second splitbushing end cap is fastened on the second end.
 70. The process of claim68 wherein the second end is flared.
 71. The process of claim 69 whereinthe first end and second end are unthreaded.
 72. The process of claim 69further comprising cooling the pipe and threading the ends.
 73. Theprocess of claim 68 wherein the split-end bushing comprises at least onecurved section.
 74. A pipe produced by the process of claim
 68. 75. Aprocess for boronizing a metal pipe comprising an unthreaded first end,an unthreaded second end, an interior, an inside surface and an outsidesurface; fastening a first plate to the first end of the pipe; placingboronizing powder in the interior of the pipe; fastening a second plateto the second end of the pipe; heating the pipe to a temperature from1400° F. to 1900° F., thereby forming a borided layer on the insidesurface, and generating spent reaction gases and spent boriding powder.76. The process of claim 73 wherein the first plate and second plate arefastened onto the ends of the pipe by welding or joining.
 77. A processcomprising: placing a boronizing powder composition in a metal pipecomprising a first end, a second end, an inside surface and an outsidesurface; heating the pipe to form a borided layer on the inside surface,and spent boronizing powder; heating the pipe with the borided layer toabove its austenitizing temperature, thereby forming an austenitizedpipe; quenching the austenitized pipe, thereby forming a quenched pipe;and tempering the quenched pipe, thereby forming a tempered pipe.